The Race Face chain rings I have on are pretty new and a long way from needing replacement and the BB I have is functioning perfectly and doesn't need replacing either. I am also aware of the Sugino XD300 crankset if Profile Racing doesn't come to the party and replace the right arm which is cracked where it interfaces with the BB.

I mean, really, the only reason for 4 bolt cranks in the first place for Shimano to stick it to the consumer and all the aftermarket companties.

Every, major, mountain bike crank manufacturer, has standardized at 104mm / 64mm, 4 arm, with outside BB bearings.
I got curious and searched for quite awhile. Almost everything was 104 / 64.
I couldn't find anything that was square taper, except Sugino and a couple of really crappy cranksets.
Even the old square taper Deore cranks are gone. I couldn't even find some low end Truvative square taper, much less 5 arm.

Amp B-4s are classic bikes, so I don't blame the OP for wanting to keep a retro look.

It also appears that Middleburn have a Spider for their RS8 to suit 110/74 rings for which I'm awaiting confirmation but it's no where near as light as my old Profile Racing cranks which are 400 grams for 175mm length including the spider but without bolts or rings.

It also appears that Middleburn have a Spider for their RS8 to suit 110/74 rings for which I'm awaiting confirmation but it's no where near as light as my old Profile Racing cranks which are 400 grams for 175mm length including the spider but without bolts or rings.

Something to keep in mind, is that the new weights for cranksets, include everything, including the BB.
I don't blame you for wanting to keep the old cranks, but the new ones from Shimano, Raceface, etc really are light years ahead of cranks from just a few years ago.
The outside BBs are a huge improvement in reliability over the old UN and ISIS internal bearings.

Another thing to consider is the Q-factor. The Profile Racing cranks were Low Profile and even then my heels would sometimes rub on them.

So, if a set of Crankarms using Outboard bearings were to be the final solution which would provide the lowest Q-factors?

Otherwise it looks like maybe the Sugino or TA Carmina with a lightweight BB such as American Classic or Phil Wood could be the best option.

Hmmmm...I don't know who has the lowest "Q" factor.
I'm a big guy at 6' 1" and look for wider cranks.
I do have a heel rubbing problem though, because I ride with my toes pointed outward and I haven't had any issues with my LX Hollowtech II cranks. The XTs are nice as well.
I haven't rode them, but a lot of riders around Bootleg love Race Face as well.
Around here, we have started to think of Truvative as an OEM brand, with hit or miss quality issues. Truvative's, freeriding and DH cranks are overly heavy, but they are strong though.

Besides Profile Racing are there any other options for 5 bolt 110/74 BCD cranks?

See if you can find some Race Face Turbines - these are 110/74, running Blackspire Super Pro rings - awesome setup. Light enough, strong too. To run an inner ring, you'll need to buy some 8.3mm spacers too - but those are easy to source.

I don't blame you for wanting to keep the old cranks, but the new ones from Shimano, Raceface, etc really are light years ahead of cranks from just a few years ago.
The outside BBs are a huge improvement in reliability over the old UN and ISIS internal bearings.

What's the huge improvement over the bearings of a Shimano UN-xx square taper bottom bracket?

*crickets chirping*

Sure, the new x-type is light years ahead of ISIS, only because ISIS had smaller bearings, but ISIS was a solution looking for a problem. Square taper with good quality bearings simply do not have problems. You certainly wouldn't have a sticky at the top of a forum telling all the johnny come lately's how to fix their creaky, gritty square taper BB's. I'm tempted to pull the plug and finally upgrade to x-type, but I keep finding reasons to enjoy the reliability of the good old square taper.